# Build a Recycling-Sorting Machine

6th-8th
Group Size
2-3 students
Active Time
2 hours
Total Time
2 hours
Area of Science
Physics
Key Concepts
Forces, magnetism, engineering design
Learning Objectives
• Understand that magnets exert forces even when they are not in contact with each other
• Understand the factors that affect the strength of magnetic forces
• Evaluate competing design solutions using the same criteria
Credits
Ben Finio, PhD, Science Buddies

a recycling sorting machine. A plastic cup holds paper clips and shreds of paper. A vertical cardboard tube supports a downward carboard ramp. The ramp feeds into a plastic bottle lined with magnets, which feeds into a plastic cup.

## Overview

In this lesson plan, your students will build their own recycling sorting machines that use various methods, like magnets or puffs of air, to separate shreds of paper from paper clips. This lesson is inspired by the real-world engineering challenge of separating various materials, like paper, plastic, and metals, that get combined in single-stream recycling programs.

## NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
• MS-PS2-3. Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.
• MS-PS2-5. Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.
• MS-ETS1-2. Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
This lesson focuses on these aspects of NGSS Three Dimensional Learning:

 Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts Constructing Explanations and Designing Solutions. Apply scientific ideas or principles to design an object, tool, process or system. Engaging in Argument from Evidence. Evaluate competing design solutions based on jointly developed and agreed-upon design criteria. PS2.B: Types of Interactions. Electric and magnetic (electromagnetic) forces can be attractive or repulsive, and their sizes depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distances between the interacting objects. Forces that act at a distance (electric, magnetic, and gravitational) can be explained by fields that extend through space and can be mapped by their effect on a test object (a charged object, a magnet, or a ball, respectively). ETS1.B: Developing Possible Solutions. There are systematic processes for evaluating solutions with respect to how well they meet the criteria and constraints of a problem. Influence of Science, Engineering, and Technology on Society and the Natural World. The uses of technologies and limitations of their use are driven by individual or societal needs, desires, and values; by the findings of scientific research; and by differences in such factors as climate, natural resources, and economic conditions.

## Materials

• Paper clips
• Paper
• Magnets
• Scissors
• Cardboard
• Tape
• Cups
• Optional: other construction/craft materials such as wooden craft sticks, glue, pipe cleaners, etc.

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6th-8th
Group Size
2-3 students
Active Time
2 hours
Total Time
2 hours
Area of Science
Physics
Key Concepts
Forces, magnetism, engineering design
Credits
Ben Finio, PhD, Science Buddies
Learning Objectives
• Understand that magnets exert forces even when they are not in contact with each other
• Understand the factors that affect the strength of magnetic forces
• Evaluate competing design solutions using the same criteria
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